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Vision Loss Concerns with new Anti-Seizure Medication

Monday November 2, 2009
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Sabril (vigabatrin) oral solution was recently approved by the FDA in liquid form for the treatment of infantile spasms in children ages 1 month to 2 years. It is the first drug in the U.S. approved to treat this severe, often debilitating disorder characterized by frequent difficult-to-control daily seizures. Spasms tend to occur upon awakening or after feeding, and often occur in clusters of up to 100 spasms. Infants may have dozens of clusters and several hundred spasms per day. The drug is available in packets containing 500mg of powdered medication that may only be reconstituted with 10 ml of cold or room-temperature water. Infant dosing is based on weight but must never exceed 150 mg/kg/day.

Sabril (vigabatrin) tablets also have been approved for adult use in combination with other medications to treat complex partial seizures that have not responded adequately to previous drug therapies. The drug is available as 500 mg tablets that are typically initially prescribed twice daily and titrated up to a dose of 1.5 grams twice daily. Patients with renal impairment may require a dosage reduction.

Although effective in seizure control, vigabatrin carries a black box warning because of unavoidable vision impairment that occurs with use of the drug. Even with the lowest dose prescribed, patients risk a progressive loss of peripheral vision and a potential decrease in visual acuity. Vision changes are permanent and may continue even after the drug has been discontinued.

Because of the risk of permanent vision loss, vigabatrin is only available through a restricted distribution program.

Other adverse effects, in addition to vision loss, include anemia, weight gain, edema, and fatigue. More serious adverse effects include peripheral neuropathy and the risk of suicidal thoughts and behavior.

Remind parents of infants and patients treated with vigabatrin not to abruptly discontinue the medication because withdrawal seizures may occur. Itís also crucial to emphasize that the medication must be securely stored and clearly labeled to avoid inadvertent administration to anyone other than the patient.

Because of the restricted distribution, patients treated with vigabatrin may be required to bring their own supply of medication with them to treatment facilities. Many hospital and healthcare facility pharmacies have procedures to accommodate special medications that arenít ordinarily part of their routine formulary. In places where medication management is solely controlled by nurses, itís crucial for them to become familiar with this medication and take special precautions to avoid administration errors.

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